Process for producing 1,3-dialkyl-2-imidazolidinone compound

ABSTRACT

There is provided a process for preparing a 1,3-dialkyl-2-imidazolidinone by using an alkylene oxide as a first component, using at least one of (A) carbon dioxide and a monoalkylamine; (B) a carbon dioxide compound of the monoalkylamine; and (C) an 1,3-dialkylurea, reacting the first and second components by heating at 50 ° C. or higher to give 1,3-dialkyl-2-imidazolidinone, characterized in that the total molar amount of a molar feed amount of the monoalkylamine included in the component (A), a molar feed amount of the monoalkylamine part of the carbon dioxide compound of monoalkylamine, component (B), and the double of a molar feed amount of the 1,3-dialkylurea, component (C), is at least three folds of a molar feed amount of the alkylene oxide.  
     The preparation process of this invention uses an industrially readily available alkylene oxide as a starting material and can be suitably conducted with a higher yield in an industrial scale.

TECHNICAL FIELD

[0001] This invention relates to a process for preparing1,3-dialkyl-2-imidazolidinones.

[0002] 1,3-Dialkyl-2-imidazolidinones have been widely used as anaprotic polar solvent. For example, they are useful as a solvent for aresin such as polyamides, polyesters, polyvinyl chlorides and phenolresins; a solvent for a variety of organic synthetic reactions; or anextraction solvent for extracting an aromatic hydrocarbon from a mixtureof hydrocarbons. Among those, 1,3-dimethyl-2-imidazolidinone(hereinafter, sometimes referred to as “DMI”) is particularly usefulbecause it exhibits particularly higher resistance to a strong alkaliand thus is little decomposed even when heated with an alkali-metalhydroxide solution. It is, therefore, also preferred as a solvent fordehalogenation of an aromatic organohalide.

BACKGROUND ART

[0003] Various processes using N,N′-dimethylethylenediamine as astarting material have been proposed for preparing1,3-dialkyl-2-imidazolidinones; for example, reactingN,N′-dimethylethylenediamine with trichloromethyl chloroformate (JP-A53-73561); reacting N,N′-dimethylethylenediamine with carbon dioxide(JP-A 57-175170); reacting N,N′-dimethylethylenediamine with phosgene inthe presence of water and a dehydrochlorinating agent (JP-A 61-109772and JP-A 61-172862); and reacting N,N′-dialkylethylenediamine with ureain a polar solvent (JP-A 7-252230). A known process for preparingN,N′-dialkylethylenediamines as a starting material such asN,N′-dimethylethylenediamine described above is based on ethylenedichloride and monomethylamine as described in JP-A 57-120570. Theprocess, however, produces a large amount of salt contaminated withorganic compounds as a byproduct, which may cause a difficult issue ofdisposal. J. Organometallic Chem., 407, 97 (1991) has described aprocess where ethylene glycol is reacted with monomethylamine in thepresence of a homogeneous catalyst comprising ruthenium andtriphenylphosphine. Recovery and recycle of a homogeneous noble metalcatalyst is, however, industrially difficult. Therefore, a process usingN,N′-dialkylethylenediamine as a starting material is not ideal forpreparing 1,3-dialkyl-2-imidazolidinone.

[0004] In addition, there have been proposed reduction of2-imidazolidinone and formaldehyde in the presence of a hydrogenationcatalyst (JP-A 60-243071) and catalytic reduction ofN,N′-hydroxymethylimidazolidinone dialkyl ether (JP-B 60-3299). Theseprocesses, however, employ a starting material derived fromethylenediamine. which may also cause the problem described above, andare impractically longer processes.

[0005] Alternative processes have been disclosed, including reacting anN-alkylmonoethanolamine and an alkylamine such as monomethylamine withcarbon dioxide, an alkylamine alkylcarbamate or 1,3-dialkylurea (JP-A57-98268); reacting ethylene glycol, carbon dioxide and monomethylamineat an elevated temperature under a higher pressure (JP-A 59-155364); andreacting alkylene carbonate with monoalkylamine (JP-A10-502917). Theseprocesses are one-step processes, and an N-alkylmonoethanolamine,ethylene glycol and an alkylene carbonate as starting materials can bereadily prepared from an alkylene oxide. These processes are, therefore,noteworthy. These processes have a problem of production ofN-alkyldiethanolamines as byproducts during preparing anN-alkylmonoethanolamine from ethylene oxide. JP-A 10-330366 hasdisclosed a process for preparing DMI by a one-pot reaction fromethylene oxide, which has a problems of a lower yield.

[0006] In these processes, a monoalkylamine as a starting material isdisproportionated during a reaction to give disproportionationbyproducts, i.e., ammonia, a dialkylamine and/or a trialkylamine. JP-B1-15503 has disclosed a process where ethylene glycol is used as astarting material and unreacted materials containing a monoalkylamine iscirculated and recycled in a reactor. In this process, ammonia as abyproduct is also circulated so that repeated circulation may increaseammonia, leading to increase of byproducts such as1-alkyl-2-imidazolidinones and reduction in an yield of desired1,3-dialkyl-2-imidazolidinones. Thus, this process has not beenindustrially available.

DISCLOSURE OF THE INVENTION

[0007] An objective of this invention is to provide a process forpreparing 1,3-dialkyl-2-imidazolidinones using an industrially readilyavailable alkylene oxide as a starting material with an improved yieldwhich can be suitably practicable in an industrial scale. Anotherobjective of this invention is to provide a process for highlyeffectively preparing 1,3-dialkyl-2-imidazolidinones by effectivelyseparating or processing byproducts such as N-alkyldiethanolamines,ammonia, dialkylamines, trialkylamines, 1-alkyl-2-imidazolidinones and1,3-dialkylureas.

[0008] The inventors have conducted intense investigation for solvingthe above problems and have found that these problems can be solved by aprocess for preparing 1,3-dialkyl-2-imidazolidinones by heating a firstcomponent consisting of an alkyleneoxide and a second componentconsisting of at least one of (A) carbon dioxide and a monoalkylamine,(B) a carbon dioxide compound of a monoalkylamine and (C) a1,3-dialkylurea at 50° C. or higher, wherein the second component ischarged such that the total of a molar amount of the chargedmonoalkylamine in the component (A), a molar amount of themonoalkylamine part in the charged carbon dioxide compound ofmonoalkylamine, component (B), and the double of a molar amount of thecharged 1,3-dialkylurea, component (C), is at least three folds of amolar amount of the charged alkylene oxide, achieving this invention.

[0009] This invention provides a process for preparing a1,3-dialkyl-2-imidazolidinone by using an alkylene oxide represented byformula (1) as a first component:

[0010] wherein in the formula (1), R¹ represents hydrogen or alkyl grouphaving 1 to 6 carbon atoms,

[0011] using at least one selected from the group consisting of thefollowing components (A), (B) and (C) as a second component:

[0012] component (A): carbon dioxide and a monoalkylamine represented byformula (2):

R²NH₂  (2)

[0013] wherein in the formula (2), R²represents alkyl group having 1 to6 carbon atoms;

[0014] component (B): a carbon dioxide compound of the monoalkylaminerepresented by formula (2); and

[0015] component (C): an 1,3-dialkylurea represented by formula (3):

R²NHCONHR²  (3)

[0016] wherein in the formula (3), R² is as defined above,

[0017] and reacting said first component with said second component byheating those components at 50° C. or higher to give1,3-dialkyl-2-imidazolidinone represented by formula (4):

[0018] wherein in the formula (4), R¹ and R² are as defined above,

[0019] characterized in that the total molar amount of a molar feedamount of the monoalkylamine included in the component (A), a molar feedamount of the monoalkylamine part of the carbon dioxide compound ofmonoalkylamine, said compound being component (B), and the double of amolar feed amount of the 1,3-dialkylurea, said 1,3-dialkylurea beingcomponent (C), is at least three folds of a molar feed amount of saidalkyleneoxide.

[0020] The reaction is preferably conducted under a pressure of 4 MPa orhigher.

[0021] It is also preferable that the total molar amount of a molar feedamount of the carbon dioxide included in the component (A), a molar feedamount of the carbon dioxide part of the carbon dioxide compound ofmonoalkylamine, said compound being the component (B) and a molar feedamount of the 1,3-dialkylurea, said 1,3-dialkylurea being the component(C), is at least one and half folds of a molar feed amount of saidalkylene oxide.

[0022] It is also preferable that R¹ is hydrogen atom; R² representsmethyl; and the 1,3-dialkyl-2-imidazolidinone prepared is1,3-dimethyl-2-imidazolidinone.

[0023] In this process, it is also preferable that ethylene oxide isused as said first component and at least one selected from the groupconsisting of the following components (D), (E) and (F) is used as saidsecond component:

[0024] component (D): carbon dioxide and monomethylamine;

[0025] component (E): a carbon dioxide compound of monomethylamine; and

[0026] component (F): 1,3-dimethylurea,

[0027] the process comprises:

[0028] (1) a 1,3-dimethyl-2-imidazolidinone preparation step ofpreparing 1,3-dimethyl-2-imidazolidinone by heating said first componentand said second component at 50° C. or higher,

[0029] and the process further comprises:

[0030] (2) a first separation step of separating the reaction mixtureobtained in the 1,3-dimethyl-2-imidazolidinone preparation step into

[0031] a first fraction containing monomethylamine, carbon dioxide and acarbon dioxide compound of monomethylamine as main components, and alsocontaining water; and

[0032] a second fraction containing 1,3-dimethyl-2-imidazolidinone andhigh-boiling compounds with a higher boiling point than that of1,3-dimethyl-2-imidazolidinone as main components, and also containingwater;

[0033] (3) a second separation step of separating at least part of thesecond fraction in the first separation step into

[0034] a first fraction containing water and low-boiling amines with aboiling point higher than that of water and lower than that of1,3-dimethyl-2-imidazolidinone as main components; and

[0035] a second fraction containing 1,3-dimethyl-2-imidazolidinone andsaid high-boiling compounds as main components;

[0036] (4) a third separation step of separating the second fraction inthe second separation step into

[0037] a first fraction containing 1,3-dimethyl-2-imidazolidinone as amain component; and

[0038] a second fraction containing said high-boiling compounds as maincomponents; and

[0039] (5) a fourth separation step of separating the first fraction inthe first separation step into

[0040] a first fraction containing ammonia, dimethylamine,trimethylamine, a carbon dioxide compound of ammonia, a carbon dioxidecompound of dimethylamine and a carbon dioxide compound oftrimethylamine as main components, and also containing water; and

[0041] a second fraction containing monomethylamine and a carbon dioxidecompound of monomethylamine as main components, and also containingwater,

[0042] where at least part of the second fraction in the fourthseparation step is supplied in the 1,3-dimethyl-2-imidazolidinonepreparation step.

[0043] Furthermore, the above 1,3-dimethyl-2-imidazolidinone preparationstep may be carried out by:

[0044] (6) a first reaction step of heating ethylene oxide and at leastone selected from the group consisting of the components (D), (E) and(F) at 50° C. or higher to prepare N-methyldiethanolamine and2-(methylamino)ethanol; and

[0045] (7) a second reaction step of heating N-methyldiethanolamine and2-(methylamino)ethanol prepared in the first reaction step with at leastone selected from the group consisting of the components (D), (E) and(F) at 100° C. or higher to prepare 1,3-dimethyl-2-imidazolidinone, and

[0046] the second fraction in the fourth separation step may be suppliedin said first reaction step and/or said second reaction step.

[0047] In the fourth separation step, at least part of the firstfraction in the first separation step may be contacted with carbondioxide, heated at 50° C. or higher, and separated by vapor-liquidseparation to remove the first fraction in the fourth separation stepinto the gaseous phase and obtain the second fraction in the fourthseparation step from the liquid phase.

BRIEF DESCRIPTION OF DRAWINGS

[0048]FIG. 1 is a block diagram showing an embodiment of a preparationprocess according to this invention.

[0049]FIG. 2 is a block diagram showing another embodiment of apreparation process according to this invention.

[0050]FIG. 3 is a block diagram showing another embodiment of apreparation process according to this invention.

[0051]FIG. 4 is a block diagram showing another embodiment of apreparation process according to this invention.

[0052] In these drawings, symbols represent the followings: 1: the1,3-dimethyl-2-imidazolidinone preparation step; 2: the first separationstep; 3: the second separation step; 4: the third separation step; 5:the fourth separation step; 6: the first reaction step; 7: the secondreaction step; 8: a seventh separation step; 9: a hydrolysis step; 10:an absorption step; 11: a fifth separation step; 12: a rectificationstep; 13: a sixth separation step.

BEST MODE FOR CARRYING OUT THE INVENTION

[0053] Hereinafter, this invention will be described in detail.

[0054] This invention provides a process for preparing a1,3-dialkyl-2-imidazolidinone.

[0055] According to the process of this invention, the1,3-dialkyl-2-imidazolidinone is prepared by reacting the firstcomponent consisting of an alkylene oxide represented by the formula(1); and the second component consisting of at least one selected fromthe group consisting of:

[0056] component (A):carbon dioxide and a monoalkylamine represented bythe formula (2);

[0057] component (B): a carbon dioxide compound of the monoalkylaminerepresented by the formula (2);

[0058] component (C): a 1,3-dialkylurea represented by the formula (3),by heating those components at 50° C. or higher.

[0059] An alkylene oxide used as a starting material in the process ofthis invention is an alkylene oxide in which a straight or circularalkyl group represented by R¹ has 1 to 6 carbon atoms, including, forexample, ethylene oxide, propylene oxide, ethyloxirane, propyloxirane,(1-methylethyl)oxirane, cyclopropyloxirane, (1,1-dimethylethyl)oxirane,n-butyloxirane, (2-methylpropyl)oxirane, (1-methylpropyl)oxirane,(1-methylcyclopropyl)oxirane, (1,2-dimethylpropyl)oxirane,n-pentyloxirane, (2-methylbutyl)oxirane, (1-ethylpropyl)oxirane,(3-methylbutyl)oxirane, (1-methylbutyl)oxirane,(2,2-dimethylpropyl)oxirane, cyclopentyloxirane,(3,3-dimethylbutyl)oxirane, (1,1-dimethylbutyl)oxirane,(1-methylpentyl)oxirane, n-hexyloxirane, cyclopentylmethyloxirane andcyclohexyloxirane. Among these, ethylene oxide or propylene oxide ispreferable and ethylene oxide is more preferable because a1,3-dialkyl-2-imidazolidinone or 1,3-dialkylpropyleneurea as a producthas a variety of applications.

[0060] A monoalkylamine represented by the formula(2) which is one ofthe second component in this invention, is amonoalkylamine in which astraight or circular alkyl group represented by R² has 1 to 6 carbonatoms, including, for example, monomethylamine, monoethylamine,mono(n-propyl)amine, mono (iso-propyl) amine, mono (n-butyl) amine, mono(sec-butyl) amine, mono(iso-butyl) amine, mono (tert-butyl) amine, mono(n-amyl) amine, mono(1-methylbutyl)amine, mono(2-methylbutyl)amine, mono(iso-amyl) amine, mono (tert-amyl) amine, mono(neo-pentyl)amine, mono(1,2-dimethylpropyl) amine, mono(1-ethylpropyl)amine, mono (n-hexyl)amine and monocyclohexylamine. Among these, monomethylamine ormonoethylamine is preferable and monomethylamine is more preferablebecause 1,3-dimethyl-2-imidazolidinones or1,3-diethyl-2-imidazolidinones have a variety of applications.

[0061] A carbon dioxide compound of monoalkylamine, wich is one of thesecond component in the process of this invention, includes, forexample, carbonates, hydrogencarbonates and alkyl carbamates ofmonoalkylamine.

[0062] The carbon dioxide compound of monoalkylamine may be used as asolid or a solution such as an aqueous solution. Alternatively,components which generate the carbon dioxide compound in the reactionsystem can be used in combination.

[0063] 1,3-Dialkylurea represented by the formula (3) which is one ofthe second component in the process of this invention, is1,3-dialkylurea in which an alkyl group represented by R² has 1 to 6carbon atoms, including, for example, 1,3-dimethylurea, 1,3-diethylurea,1,3-di(n-propyl)urea, 1,3-di(iso-propyl)urea, 1,3-di(n-butyl)urea,1,3-di(sec-butyl)urea, 1,3-di(iso-butyl)urea, 1,3-di(tert-butyl)urea,1,3-di(n-amyl)urea, 1,3-di(1-methylbutyl)urea,1,3-di(2-methylbutyl)urea, 1,3-di(iso-amyl)urea, 1,3-di(tert-amyl)urea,1,3-di(neo-pentyl)urea, 1,3-di(1,2-dimethylpropyl)urea,1,3-di(1-ethylpropyl)urea, 1,3-di(n-hexyl)urea and 1,3-dicyclohexylurea.Among these, 1,3-dimethylurea or 1,3-diethylurea is preferable and1,3-dimethylurea is more preferable because a1,3-dialkyl-2-imidazolidinone or 1,3-dialkylpropyleneurea as a producthas a variety of applications.

[0064] The 1,3-dialkylurea may be used as is commercially available oras a solution such as an aqueous solution. Alternatively, componentswhich generate the 1,3-dialkylurea in the reaction system may be used incombination.

[0065] The amount of the second component supplied for the reaction inthe process of this invention is determined such that the total molaramount of the following i) to iii) included in the second componentrecovered and recycled and in the second component newly supplied to areactor is preferably at least three folds, more preferably 3 to 40folds both inclusive of the molar amount of the alkylene oxide:

[0066] i) the molar amount of the monoalkylamine;

[0067] ii) the molar amount of the monoalkylamine part in the carbondioxide compound of the monoalkylamine and

[0068] iii) the double of the molar amount of 1,3-dialkylurea.

[0069] The reaction can be conducted under the conditions departing fromthe above range, but the total molar amount of less than three folds maylead to reduction in an yield of the 1,3-dialkyl-2-imidazolidinone. Thetotal molar amount of more than 40 folds may be disadvantageous becauseof reduction in a volumetric efficiency of a reactor, and increase in acost for recovery of the unreacted monoalkylamine, carbon dioxidecompound of the monoalkylamine and 1,3-dialkylurea. Without recoveringand recycling, it is sufficient to consider only the second componentnewly supplied into the reactor.

[0070] Since DMI as a product has a variety of applications as asolvent, it is most preferable to use ethylene oxide as an alkyleneoxide, monomethylamine as a monoalkylamine, a carbon dioxide compound ofmonomethylamine as a carbon dioxide compound of monoalkylamine, and1,3-dimethylurea as a 1,3-dialkylurea.

[0071] In a reaction in the process of this invention, a reaction systemcan be replaced or pressurized with a gas.

[0072] In terms of a pressure, a pressure at a reaction temperature ispreferably 4 MPa or higher. Although the reaction may be conducted at apressure of less than 4 MPa, it may be disadvantageous because oftendency to reduction in a production efficiency of a1,3-dialkyl-2-imidazolidinone.

[0073] As a gas for replacement or pressurization as described above,carbon dioxide is preferable because it can be also used as the secondcomponent, but another gas including an inert gas such as nitrogen andargon can be appropriately used. Using carbon dioxide results inimprovement in an yield of a 1,3-dialkyl-2-imidazolidinone. Carbondioxide may be used as gaseous, liquid, solid or supercritical carbondioxide. The amount of carbon dioxide supplied in this reaction isdetermined such that the total molar amount of carbon dioxide used fordisplacement or pressurization and the following iv) to vi) included inthe second component recovered and recycled and in the second componentnewly supplied is preferably at least one and half folds, morepreferably 4 to 100 folds both inclusive of the molar amount of thealkylene oxide supplied:

[0074] iv) the molar amount of carbon dioxide;

[0075] v) the molar amount of carbon dioxide part in the carbon dioxidecompound of alkylamine; and

[0076] vi) the molar amount of 1,3-dialkylurea.

[0077] The total molar amount of less than one and half folds isdisadvantageous because of tendency to reduction in a productionefficiency for the 1,3-dialkyl-2-imidazolidinone, while the total molaramount of more than 100 folds may be disadvantageous because of tendencyto reduction in a volumetric efficiency of the reactor.

[0078] A reaction in the process of this invention is conducted at 50°C. or higher, preferably 50 to 300° C. both inclusive. A temperature oflower than 50° C. may be disadvantageous because of tendency toreduction in a production efficiency for the1,3-dialkyl-2-imidazolidinone, while a temperature of higher than 300°C. may be disadvantageous because of tendency to increase in byproducts.

[0079] A reaction time depends on factors such as the amounts ofstarting materials and a reaction temperature; preferably 200 hours orless, more preferably 0.01 to 100 hours both inclusive, furtherpreferably 0.1 to 50 hours both inclusive. A time of less than 0.01hours may be disadvantageous because of tendency to reduction in anyield of a 1,3-dialkyl-2-imidazolidinone, while a time of more than 200hours may be disadvantageous because of tendency to reduction in avolumetric reaction efficiency.

[0080] A reaction in the process of this invention may be conducted neator sometimes using a solvent. Any solvent which is inert to reactionsubstrates under the reaction condition may be used; preferably, water,hydrocarbons, ethers, amides, circular ureas and supercritical carbondioxide. Among these, water or a 1,3-dialkyl-2-imidazolidinone which isidentical to the product is more preferable because it can eliminate anadditional step of recovering a solvent because it is a reactionproduct.

[0081] These solvents may be used alone or in combination of two ormore. Depending on a solvent used, the reaction may be conducted in amultiphase system of two or more phases.

[0082] The solvent may be suitably used in an amount sufficient todissolve a part of at least one of the starting materials used. Theamount is preferably 100 parts by weight or less, more preferably 50parts by weight or less to one part by weight of an alkylene oxide as astarting material. An amount of more than 100 parts by weight isdisadvantageous because of tendency to reduction in a volmetricefficiency.

[0083] In the process of this invention, a catalyst or additive may beused for further improving an yield or reaction rate.

[0084] A reactor used for a reaction in the process of this inventionmay be made of an appropriate known material, and a reactor whose innerwall is at least partly made of the following material (I) is preferablebecause it may provide a 1,3-dialkyl-2-imidazolidinone with a higheryield:

[0085] (I) a metal and/or its oxide containing at least one selectedfrom the group consisting of titanium and zirconium.

[0086] Examples of such a reactor include those totally made of a metalcontaining titanium or zirconium; those whose inner wall is at leastpartly coated with a metal or its oxide containing titanium orzirconium; and those whose inner wall is coated with an inorganic glass.Examples of a metal containing titanium or zirconium include industrialpure titanium in JIS Groups 1 to 4; anticorrosion titanium alloys suchas Ti-0.15Pd, Ti-5Ta and Ti-0.3Mo-0.8Ni; α-type titanium alloys such asTi-2.5Sn, Ti-5Al-2.5Sn, Ti-5Al-2.5Sn(ELI), Ti-2.5Cu, Ti-2O-1N-5Fe,Ti-5Ni-0.5Ru, Ti-0.5Pd-3Co and Ti-5.5Al-3.5Sn-3Zr-1Nb-0.3Mo-0.3Si; nearα-type titanium alloys such as Ti-8Al-1Mo-1V,Ti-2.25Al-11Sn-5Zr-1Mo-0.2Si, Ti-6Al-2Sn-4Zr-2Mo,Ti-5Al-5Sn-2Zr-2Mo-0.25Sn, Ti-6Al-2Nb-1Ta-0.8Mo, Ti-6Al-5Zr-0.5Mo-0.2Siand Ti-4.5Al-3V-2Fe-2Mo; α+β-type titanium alloys such asTi-5Al-2Cr-1Fe, Ti-5Al-5Sn-5Zr-2Cr-1Fe, Ti-4Al-4Mn, Ti-3Al-2.5V,Ti-6Al-4V, Ti-6Al-4V(ELI), Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo,Ti-7Al-4Mo, Ti-5Al-2Zr-4Mo-4Cr, Ti-6Al-1.7Fe-0.1Si, Ti-6.4Al-1.2Fe,Ti-15Zr-4Nb-2Ta-2Pd, Ti-6Al-7Nb and Ti-8Mn; β-type titanium alloys suchas Ti-13V-11Cr-3Al, Ti-15Mo-5Zr, Ti-15Mo-0.2Pd, Ti-15V-3Cr-3Sn-3Al,Ti-20V-4Al-1Sn, Ti-22V-4Al and Ti-16V-4Sn-3Al-3Nb; near β-type titaniumalloys such as Ti-10V-2Fe-3Al and Ti-9.5V-2.5Mo-3Al; zirconium alloyssuch as zircaloy-2, zircaloy-4, Zr-2.5Nb and ozenite. Among thesemetals, titanium-containing metals are preferable and industrial puretitanium or an anticorrosion titanium alloy is more preferable.

[0087] In the process of this invention, an alkylene oxide and amonoalkylamine are reacted to give a 1,3-dialkyl-2-imidazolidinone viacorresponding N-alkylmonoethanolamine and N-alkyldiethanolamine asintermediates. According to the process of this invention, a1,3-dialkyl-2-imidazolidinone can be, therefore, prepared by forming anN-alkylmonoethanolamine and N-alkyldiethanolamine at 50° C. or higherand then reacting these products at a further higher temperature. Insuch a case, the 1,3-dialkyl-2-imidazolidinone may be formed not onlyfrom the N-alkylmonoethanolamine but also from theN-alkyldiethanolamine. Thus, it is not necessary to separate these.

[0088] Any style of the process of this invention may be employed aslong as starting materials used can be effectively mixed and contactedwith other material. Any of batch, semi-batch and continuous flowsystems may be employed; for example, charging all materials together ina reactor, continuous or intermittent feeding of at least one materialinto the other materials, or continuously or intermittently feeding allmaterials. Alternatively, after mixing the first component and a part ofthe second component, then the mixture may be fed into a reactor. Insuch a case, a reaction may proceed in a feed line, and anN-alkylmonoethanolamine and/or an N-alkyldiethanolamine may be formed inthe line.

[0089] In the process of this invention, a product solution may be, ifnecessary, treated as usual, for example, by distillation orcrystallization to provide a desired 1,3-dialkyl-2-imidazolidinone.

[0090] When a 1,3-dialkyl-2-imidazolidinone prepared by the process ofthis invention is DMI, it is preferably prepared according to a processflow shown in FIG. 1 or 2. FIGS. 3 and 4 show the embodiments in FIGS. 1and 2 with additional steps for further improving a productionefficiency or purity for DMI.

[0091] This invention will be described with reference to FIGS. 3 and 4.

[0092] As shown in FIG. 3, in 1,3-dimethyl-2-imidazolidinone preparationstep (1), ethylene oxide, monomethylamine as one compound of thecomponent (D) and carbon dioxide as another compound of the component(D) are fed to the 1,3-dimethyl-2-imidazolidinone preparation step vialines L1, L2 and L3, respectively. The components (E) and/or (F) may beused in place of or in addition to the component (D). In such a case, acarbon dioxide compound of monomethylamine as the component (E) is fedto the 1,3-dimethyl-2-imidazolidinone preparation step via line 52,while 1,3-dimethylurea as the component (F) is fed via line 53. Ethyleneoxide, monomethylamine, carbon dioxide, the carbon dioxide compounds ofmonomethylamine and 1,3-dimethylurea may be fed by mixing at least twoof these in line L5 before introducing to the preparation step (1) or bydirectly introducing into a reactor without line L5. When employingmixing in line L5, line L5 may be heated for promoting a reaction in theline.

[0093] In these figures, EO represents ethylene oxide; mMA representsmonomethylamine; mMA-CO2 represents a carbon dioxide compound ofmonomethylamine; and DMU represents 1,3-dimethylurea.

[0094] In the 1,3-dimethyl-2-imidazolidinone preparation step, theamount of the second component supplied to the reaction is determinedsuch that the total of the following i′) to iii′) is preferably at leastthree folds, more preferably 3 to 40 folds both inclusive of the molaramount of ethylene oxide supplied. This molar ratio of less than 3 foldsmay be disadvantageous because of tendency to reduction in an yield of1,3-dimethyl-2-imidazolidinone, while that of more than 40 folds may bedisadvantageous because of increase in a cost for recovering unreactedmonomethylamine, the carbon dioxide compound of monomethylamine and1,3-dimethylurea:

[0095] i′) the total of the molar amount of monomethylamine recoveredand recycled and the molar amount of monomethylamine newly supplied;

[0096] ii′) the total of the molar amount of monomethylamine part in thecarbon dioxide compound of monomethylamine recovered and recycled andthe molar amount of monomethylamine part in the carbon dioxide compoundof monomethylamine newly supplied; and

[0097] iii′) the total of the double of the molar amount of1,3-dimethylurea recovered and recycled and the double of the molaramount of 1,3-dimethylurea newly supplied.

[0098] Carbon dioxide used in the 1,3-dimethyl-2-imidazolidinonepreparation step may be used as gaseous, liquid, solid or supercriticalcarbon dioxide. Carbon dioxide discharged from lines L20 and L22 may berecovered for recycling.

[0099] The amount of the second component supplied for this reaction isdetermined such that the total of the following iv′) to vi′) ispreferably at least one and half folds, more preferably 4 to 100 foldsboth inclusive of the molar amount of ethylene oxide supplied. Thismolar ratio of less than one and half folds is disadvantageous becauseof tendency to reduction in a production efficiency for the1,3-dialkyl-2-imidazolidinone, while the molar ratio of more than 100folds may be disadvantageous because of tendency to reduction in avolumetric efficiency of the reactor:

[0100] iv′) the total of the molar amount of carbon dioxide part in thecarbon dioxide compound of monomethylamine recovered and recycled andthe molar amount of carbon dioxide part in the carbon dioxide compoundof monomethylamine newly supplied;

[0101] v′) the total of the molar amount of 1,3-dimethylurea recoveredand recycled and the molar amount of 1,3-dimethylurea newly supplied;and

[0102] vi′) the total of the molar amount of carbon dioxide recoveredand recycled and the molar amount of carbon dioxide newly supplied.

[0103] The reaction in the 1,3-dimethyl-2-imidazolidinone preparationstep is conducted at 50° C. or higher, preferably 50 to 300° C. bothinclusive. A temperature of lower than 50° C. leads to reduction in aproduction efficiency for DMI. A temperature of higher than 300° C. maybe disadvantageous because of tendency to increase in byproducts.

[0104] A pressure depends on factors such as a temperature and startingmaterials; preferably 4 MPa to 30 MPa both inclusive. A pressure of lessthan 4 MPa may be disadvantageous because of tendency to reduction in aproduction efficiency for 1,3-dimethyl-2-imidazolidinone, while apressure of more than 30 MPa may be disadvantageous because of increasein a production cost of a reactor.

[0105] A reaction time depends on factors such as the amounts ofstarting materials and a reaction temperature; preferably 200 hours orless, more preferably 0.01 to 100 hours both inclusive, more preferably0.1 to 50 hours both inclusive. A time of less than 0.01 hours may bedisadvantageous because of tendency to reduction in an yield of1,3-dimethyl-2-imidazolidinone, while a time of more than 200 hours maybe disadvantageous because of tendency to reduction in a volumetricreaction efficiency.

[0106] In the 1,3-dimethyl-2-imidazolidinone preparation step, thereaction may be conducted in the presence of water, which is introducedvia lines L4 and L5. The amount of water supplied to the reaction isdetermined such that the amount of water recovered and recycled andwater newly supplied is preferably 100 parts by weight or less, morepreferably 50 parts by weight or less to one part by weight of ethyleneoxide supplied. The amount of more than 100 parts by weight isdisadvantageous because of reduction in a volumetric efficiency of thereactor.

[0107] The 1,3-dimethyl-2-imidazolidinone preparation step may becarried out by two steps, as shown in FIG. 4, i.e., a first reactionstep (6) for preparing 2-(methylamino)ethanol andN-methyldiethanolamine; and a second reaction step (7) for preparing DMIfrom 2-(methylamino)ethanol and N-methyldiethanolamine prepared in thefirst reaction step (6).

[0108] In this case, to the first reaction step are fed ethylene oxidevia lines L43, monomethylamine as one compound in the component (D) vialine L40 and carbon dioxide as another compound in the component (D) vialine L41. Alternatively, the component (E) and/or (F) may be used inplace of or in addition to the component (D). In such a case, the carbondioxide compound of monomethylamine as the component (E) is fed via lineL54 to the first reaction step while 1,3-dimethylurea as the component(F) is fed via line L55. Ethylene oxide, monomethylamine, carbondioxide, the carbon dioxide compound of monomethylamine and1,3-dimethylurea may be fed by mixing at least two of these in line L44before introducing to the first reaction step or by directly introducinginto a reactor without line L44. When employing mixing in line L44, lineL44 may be heated for promoting a reaction in the line.

[0109] In the first reaction step, 2-(methylamino) ethanol andN-methyldiethanolamine are prepared by conducting the reaction at 50° C.or higher. A temperature of lower than 50° C. is disadvantageous becauseof tendency to reduction in a production efficiency for2-(methylamino)ethanol.

[0110] A pressure in the first reaction step depends on factors such asa temperature and starting materials; preferably 0.4 MPa or more. Apressure of less than 0.4 MPa may be disadvantageous because of tendencyto reduction in a consumption rate for ethylene oxide.

[0111] A reaction mixture containing 2-(methylamino)ethanol andN-methyldiethanolamine prepared in the first reaction step and unreactedmonomethylamine can be directly fed via lines L45, L47 and L49 to thesecond reaction step. The reaction mixture can be fed to the secondreaction step after being fed to line L5 and being premixed with othermaterials such as monomethylamine, carbon dioxide, the carbon dioxidecompound of monomethylamine, 1,3-dimethylurea and/or water supplied viaL2, and so on.

[0112] In the process of this invention, the amount of the secondcomponent supplied to the first reaction step is determined such thatthe total molar amount of the following i″) to iii″) is preferably atleast three folds, more preferably 3 to 40 folds both inclusive of themolar amount of ethylene oxide supplied. This molar ratio of less than 3folds may be disadvantageous because of tendency to reduction in anyield of 1,3-dimethyl-2-imidazolidinone, while that of more than 40folds may be disadvantageous because of reduction in a volmetricefficiency of a reactor, and increase in a cost for recovery of theunreacted monomethylamine and the carbon dioxide compound ofmonomethylamine:

[0113] i″) the total of the molar amount of monomethylamine recoveredand recycled and the molar amount of monomethylamine newly supplied;

[0114] ii″) the total of the molar amount of monomethylamine part in thecarbon dioxide compound of monomethylamine recovered and recycled andthe molar amount of monomethylamine newly supplied in the carbon dioxidecompound of monomethylamine; and

[0115] iii″) the total of the double of the molar amount of1,3-dimethylurea recovered and recycled and the double of the molaramount of 1,3-dimethylurea newly supplied.

[0116] Carbon dioxide used in the first reaction step may be used asgaseous, liquid, solid or supercritical carbon dioxide. The amount ofthe second component supplied to the first reaction step is determinedsuch that the total molar amount of the following iv″) to vi″) ispreferably 100 folds or less of the molar amount of ethylene oxidesupplied. This molar ratio of more than 100 folds may be disadvantageousbecause of tendency to reduction in a volumetric efficiency of thereactor:

[0117] iv″) the total of the molar amount of carbon dioxide part in thecarbon dioxide-compound of monomethylamine recovered and recycled andthe molar amount of carbon dioxide part in the carbon dioxide compoundof monomethylamine newly supplied;

[0118] v″) the total of the molar amount of carbon dioxide recovered andrecycled and the molar amount of carbon dioxide newly supplied; and

[0119] vi″) the total of the molar amount of 1,3-dimethylurea recoveredand recycled and the molar amount of 1,3-dimethylurea newly supplied.

[0120] In the first reaction step, the reaction may be conducted in thepresence of water, which is introduced via line L42. The amount of watersupplied is preferably 100 parts by weight or less, more preferably 50parts by weight or less to one part by weight of ethylene oxidesupplied. The amount of more than 100 parts by weight is disadvantageousbecause of reduction in a volumetric efficiency.

[0121] The process of this invention may comprise a seventh separationstep (8). In such a case, a part or all of the reaction mixture preparedin the first reaction step may be fed to the seventh separation step vialines L45 and L46. In the seventh separation step, a first fractioncontaining unreacted monomethylamine as a main component and a secondfraction containing 2-(methylamino)ethanol and N-methyldiethanolamine asmain components are separated from the reaction mixture. The firstfraction may be circulated to the first reaction step via line L50. Thesecond fraction is fed to the second reaction step via lines L48 andL49. The second fraction may be fed to the second reaction step afterfeeding the fraction to line L5 and premixing it with other materialssuch as monomethylamine, carbon dioxide and/or water from, for example,line L2.

[0122] To the second reaction step can be fed the reaction mixtureobtained in the first reaction step via lines L47 and L49 and/or thesecond fraction in the seventh separation step via lines L48 and L49, tofeed 2-(methylamino)ethanol and N-methyldiethanolamine produced in thefirst reaction step to the second reaction step. When feeding at leastone of unreacted components (D), (E) and (F) to the second reactionstep, the second reaction step may be conducted as such. Further, to thesecond reaction step may be supplied monomethylamine via line L2, carbondioxide via line L3, the carbon dioxide compound of monomethylamine vialine L52 and/or 1,3-dimethylurea via line L53. To the second reactionstep may be supplied the reaction mixture in the first reaction step,the second fraction in the seventh separation step, monomethylamine,carbon dioxide, the carbon dioxide compound of monomethylamine,1,3-dimethylurea and/or water after mixing at least two of them.

[0123] In the second reaction step, the reaction is conducted at 100° C.or higher, preferably 100° C. to 300° C. both inclusive, preferably witha residence time of 1 to 24 hours both inclusive. A reaction temperatureof less than 100° C. is disadvantageous because of tendency to reductionin a production efficiency for 1,3-dimethyl-2-imidazolidinone while atemperature of more than 300° C. is disadvantageous because of tendencyto reduction in an yield of 1,3-dimethyl-2-imidazolidinone. A residencetime of less than 1 hour is disadvantageous because of tendency toreduction in a production efficiency for 1,3-dimethyl-2-imidazolidinonewhile a residence time of more than 24 hour is disadvantageous becauseof tendency to reduction in a volumetric efficiency of a reactor. Apressure depends on factors such as a temperature and the amounts ofstarting materials; preferably 4 MPa to 30 MPa both inclusive. Apressure of less than 4 MPa is disadvantageous because of tendency toreduction in a production efficiency for 1,3-dimethyl-2-imidazolidinonewhile a pressure of more than 30 MPa is disadvantageous because ofincrease in a production cost of a reactor.

[0124] In the process of this invention, the amount of the secondcomponent supplied to the second reaction step is determined such thatthe total molar amount of the following i″′) to iii″′) is preferably atleast two folds of the molar amount of ethylene oxide supplied to thefirst reaction step. More preferably, the amount of monomethylamine isdetermined such that the above molar ratio is 2 to 39 folds bothinclusive. The molar ratio of less than two folds may be disadvantageousbecause of tendency to reduction in an yield of1,3-dimethyl-2-imidazolidinone, while that of more than 39 folds may bedisadvantageous because of reduction in a volmetric efficiency of areactor, and increase in a cost for recovering unreactedmonomethylamine, the carbon dioxide compound of monomethylamine and1,3-dimethylurea:

[0125] i″′) the total of the molar amount of monomethylamine fed fromthe first reaction step to the second reaction step, the molar amount ofmonomethylamine recovered and recycled and the molar amount ofmonomethylamine newly supplied;

[0126] ii″′) the total of the molar amount of monomethylamine part inthe carbon dioxide compound of monomethylamine fed from the firstreaction step to the second reaction step, the molar amount ofmonomethylamine part in the carbon dioxide compound of monomethylaminerecovered and recycled and the molar amount of monomethylamine in thecarbon dioxide compound of monomethylamine newly supplied; and

[0127] iii″′) the total of the double of the molar amount of1,3-dimethylurea fed from the first reaction step to the second reactionstep, the double of the molar amount of 1,3-dimethylurea recovered andrecycled and the double of the molar amount of 1,3-dimethylurea newlysupplied.

[0128] In the process of this invention, carbon dioxide used in thesecond reaction step may be used as gaseous, liquid, solid orsupercritical carbon dioxide. The amount of the second componentsupplied to the second reaction step is determined such that the totalmolar amount of the following iv″′) to vi″′) is preferably at least 1.5folds, more preferably 4 to 100 folds both inclusive of the molar amountof ethylene oxide supplied. This molar ratio of less than 1.5 folds isdisadvantageous because of tendency to reduction in an yield of1,3-dimethyl-2-imidazolidinone, while the molar ratio of more than 100folds may be disadvantageous because of tendency to reduction in avolumetric efficiency of the reactor:

[0129] iv″′) the total of the molar amount of carbon dioxide fed fromthe first reaction step to the second reaction step, the molar amount ofcarbon dioxide recovered and recycled and the molar amount of carbondioxide newly supplied;

[0130] v″′) the total of the molar amount of carbon dioxide part in thecarbon dioxide compound of monomethylamine fed from the first reactionstep to the second reaction step, the molar amount of carbon dioxidepart in the carbon dioxide compound of monomethylamine recovered andrecycled and the molar amount of carbon dioxide part in the carbondioxide compound of monomethylamine newly supplied; and

[0131] vi″′) the total of the molar amount of 1,3-dimethylurea fed fromthe first reaction step to the second reaction step, the molar amount of1,3-dimethylurea recovered and recycled and the molar amount of1,3-dimethylurea newly supplied.

[0132] In the second reaction step, water may be introduced via line L4.The amount of water supplied is determined such that the total of waterfed from the first reaction step, water recovered and recycled in thesecond reaction step and water newly supplied is preferably 100 parts byweight or less, more preferably 50 parts by weight or less to one partby weight of ethylene oxide supplied to the first reaction step.

[0133] In the 1,3-dimethyl-2-imidazolidinone preparation step or thesecond reaction step, DMI is produced. The reaction mixture obtained inthe 1,3-dimethyl-2-imidazolidinone preparation step or the secondreaction step contains water; low-boiling amines which are amines havinga boiling point higher than that of water and lower than that of DMIsuch as 2-(methylamino)ethanol, 1,3-dimethylpiperazine andN,N′-dimethylethylenediamine; high-boiling compounds which are compoundshaving a boiling point higher than that of DMI such as 1,3-dimethylurea,1-methyl-2-imidazolidinone and N-methyldiethanolamine; ammonia and itscarbon dioxide compounds, monomethylamine, dimethylamine,trimethylamine, and carbon dioxide compounds of these amines; and carbondioxide, as byproducts or unreacted materials. Examples of a carbondioxide compound of ammonia or an amine include carbamates, carbonatesand hydrogencarbonates.

[0134] The reaction mixture in the 1,3-dimethyl-2-imidazolidinonepreparation step or the second reaction step is fed to the firstseparation step (2) via line L6.

[0135] In the first separation step, the reaction mixture obtained inthe 1,3-dimethyl-2-imidazolidinone preparation step or the secondreaction step is separated into the first fraction containingmonomethylamine, carbon dioxide and the carbon dioxide compound ofmonomethylamine as main components, and also containing water; and thesecond fraction containing DMI and the above high-boiling compounds asmain components, and also containing water. The first fraction may befed to the fourth separation step (5) via lines L7, L14, L16 and L19,while the second fraction may be fed to the second separation step (3)via lines L8, L10 and L13.

[0136] Separation in the first separation step is preferably conductedat a pressure lower than that in the 1,3-dimethyl-2-imidazolidinonepreparation step or the second reaction step. Such a lower pressure mayfacilitate vaporization of low-boiling components such asmonomethylamine and a part of water, which are fed to the fourthseparation step.

[0137] The process of this invention may comprise an absorption step(10) between the first separation step and the fourth separation step.In such a case, the first fraction in the first separation step is fedto the absorption step via lines L7, L14 and L15.

[0138] In the absorption step, the first fraction in the firstseparation step is contacted with and absorbed in a solvent fed via lineL17. The first fraction in the first separation step may be introducedto the absorption step as, for example, a gas, a liquid, a solution suchas an aqueous solution or any mixture of these. Any solvent can be usedas long as it is inert to reaction substrates in the1,3-dimethyl-2-imidazolidinone preparation step, the first reaction stepand the second reaction step. Examples of a solvent used generallyinclude water, hydrocarbons, ethers, amides and circular ureas. Amongthese, water and DMI are preferable and water is more preferable. Waterand DMI are preferable because they are a starting material or productin the 1,3-dimethyl-2-imidazolidinone preparation step or the secondreaction step, eliminating an additional recovery step. These solventsmay be used alone or in combination of two or more. Depending on asolvent used, the absorption may be conducted in a multiphase (two ormore phase) system.

[0139] A part of carbon dioxide which is not absorbed in a solvent inthe absorption step may be discharged outside of the system via lineL20.

[0140] The absorption solution in the absorption step is supplied to thefourth separation step (5) via lines L18 and L19.

[0141] In the fourth separation step, ammonia, dimethylamine,trimethylamine, the carbon dioxide compound of ammonia, the carbondioxide compound of dimethylamine, and the carbon dioxide compound oftrimethylamine produced as byproducts in the1,3-dimethyl-2-imidazolidinone preparation step or the second reactionstep are removed into line L22 as the first fraction. Monomethylamineand its carbon dioxide compound are recovered as the second fractionfrom the bottom of the separator. When using the absorption step, a partof the solvent in the absorption step is recovered as the secondfraction. The second fraction is recycled to the1,3-dimethyl-2-imidazolidinone preparation step via lines L23 and L5, orto the first reaction step and/or the second reaction step. A part ofthe second fraction may be discarded while the remaining may be recycledto the 1,3-dimethyl-2-imidazolidinone preparation step or to the firstreaction step and/or the second reaction step. The first fraction may bediscarded or undergo a disproportionation reaction to providemonomethylamine and then recycled to the 1,3-dimethyl-2-imidazolidinonepreparation step or the first reaction step and/or the second reactionstep.

[0142] The fourth separation step is preferably conducted in thepresence of carbon dioxide for improving a separation/recoveryefficiency for monomethylamine and/or its carbon dioxide compound.Carbon dioxide may be used as any of gaseous, liquid, solid orsupercritical carbon dioxide. Because, the reaction is conducted in thepresence of carbon dioxide in the 1,3-dimethyl-2-imidazolidinonepreparation step or the second reaction step, the separation in thefourth separation step can be conducted without feeding additionalcarbon dioxide. Alternatively, the first fraction in the firstseparation step or the absorption solution fed from the absorption stepcan be contacted with carbon dioxide supplied from line L21.

[0143] The fourth separation step may be conducted as a multistageprocess or combined with a distillation process. Such a multistageprocess or combination with a distillation process may improve arecovery efficiency for monomethylamine.

[0144] When the fourth separation step is conducted as a multistageprocess, the first fraction in the first separation step may be absorbedin water before being fed to a subsequent stage.

[0145] The second fraction containing DMI and the above high-boilingcompounds as main components and also containing water in the firstseparation step is generally fed to the second separation step (3) vialines L8, L10 and L13.

[0146] The process of this invention may comprise a hydrolysis step (9)between the first separation step and the second separation step. Insuch a case, 1,3-dimethylurea can be hydrolyzed by feeding the secondfraction in the first separation step to the hydrolysis step via linesL8 and L9, in which step the fraction is heated at 50° C. or higher. Thehydrolysis-reaction mixture is separated into a first fractioncontaining, as main components, monomethylamine, carbon dioxide, and thecarbon dioxide compound of monomethylamine prepared by hydrolysis andalso containing water; and a second fraction containing DMI and theabove high-boiling compounds as main components and also containingwater. The first fraction is fed to the fourth separation step via linesL11, L14, L16 and L19. When using an absorption step, the first fractionis fed to the absorption step via lines L11, L14 and L15. The secondfraction is fed to the second separation step via lines L12 and L13.

[0147] The mixture containing water and DMI fed to the second separationstep via line L13 is separated into the first fraction containing waterand low-boiling amines as main components and the second fractioncontaining DMI and the above high-boiling compounds as main components.The second fraction is fed to the third separation step (4) via lineL24. The first fraction may be discarded, or recycled to the1,3-dimethyl-2-imidazolidinone preparation step or the second reactionstep via lines L25, L26, L30 and L5, when the content of2-(methylamino)ethanol is low. When the content of2-(methylamino)ethanol is significant, at least part of the firstfraction may be recycled to the 1,3-dimethyl-2-imidazolidinonepreparation step or the second reaction step via lines L25, L26, L30 andL5. Alternatively, the fifth separation step (11) may be added forheighten the content of 2-(methylamino)ethanol in the circulatingliquid.

[0148] To the fifth separation step is fed the first fraction in thesecond separation step via lines L25 and L27. The fifth separation stepseparates the fraction into the first fraction containing water as amain component and the second fraction containing 2-(methylamino)ethanolas a main component. The second fraction is recycled to the1,3-dimethyl-2-imidazolidinone preparation step or the second reactionstep via lines L29, L30 and L5. In the fifth separation step,2-(methylamino)ethanol may be separated for effectively recycling2-(methylamino) ethanol contained in the first fraction in the secondseparation step to the 1,3-dimethyl-2-imidazolidinone preparation stepor the second reaction step. The first fraction in the fifth separationstep may be discarded, or at least part of the fraction may be recycledto the 1,3-dimethyl-2-imidazolidinone preparation step or the secondreaction step.

[0149] The mixture containing DMI and the above high-boiling compoundsfed to the third separation step (4) via line L24 is separated into afirst fraction containing DMI as a main component and a second fractioncontaining the above high-boiling compounds as main components in thethird separation step.

[0150] DMI as a desired product is obtained as the first fraction in thethird separation step. A rectification step (12) may be added forproviding DMI with a further improved purity. In such a case, the firstfraction in the third separation step is fed to the rectification stepvia line L32 and rectified in the rectification step to provide DMI witha high purity.

[0151] At least part of the second fraction in the third separation stepmay be recycled to the 1,3-dimethyl-2-imidazolidinone preparation stepor the second reaction step via lines L31, L33, L34 and L5. Circulationof the second fraction allows unreacted N-methyldiethanolamine to berecycled. Furthermore, 1,3-dimethylurea as a byproduct in the1,3-dimethyl-2-imidazolidinone preparation step or the second reactionstep may be circulated to allow 1,3-dimethylurea to be reacted withwater in the reaction system and decomposed into monomethylamine, carbondioxide and the carbon dioxide compound of monomethylamine. It can,therefore, reduce the amounts of monomethylamine and carbon dioxidenewly supplied to the 1,3-dimethyl-2-imidazolidinone preparation step orthe second reaction step.

[0152] The process of this invention may comprise the sixth separationstep (13) In such a case, the second fraction in the third separationstep is fed to the sixth separation step via lines L31 and L37. In thesixth separation step, the fraction is separated into a first fractioncontaining N-methyldiethanolamine and 1,3-dimethylurea as maincomponents and a second fraction containing compounds with a higherboiling point than that of 1,3-dimethylurea such as1-methyl-2-imidazolidinone as main components. At least part of thefirst fraction may be circulated into the 1,3-dimethyl-2-imidazolidinonepreparation step or the second reaction step via lines L39, L34 and L5.The second fraction may be discarded. Alternatively, this fraction mayundergo methylation to provide DMI and then fed to the third separationstep. The sixth separation step can allow N-methyldiethanolamine and/or1,3-dimethylurea to be effectively circulated into the1,3-dimethyl-2-imidazolidinone preparation step or the second reactionstep.

[0153] In the process of this invention, a reactor for the1,3-dimethyl-2-imidazolidinone preparation step, the first reaction stepand the second reaction step may be made of an appropriate knownmaterial, and a reactor whose inner wall is at least partly made of ametal and/or its oxide containing at least one selected from the groupconsisting of titanium and zirconium is preferable. Using such a reactormay allow DMIs to be prepared with a higher yield. Examples of such areactor include those totally made of a metal containing titanium orzirconium; and those whose inner wall is at least partly coated with ametal or its oxide containing titanium or zirconium. Examples of a metalcontaining titanium or zirconium include industrial pure titanium in JISGroups 1 to 4; anticorrosion titanium alloys such as Ti-0.15Pd, Ti-5Taand Ti-0.3Mo-0.8Ni; α-type titanium alloys such as Ti-2.5Sn,Ti-5Al-2.5Sn, Ti-5Al-2.5Sn(ELI), Ti-2.5Cu, Ti-20-1N-5Fe, Ti-5Ni-0.5Ru,Ti-0.5Pd-3Co and Ti-5.5Al-3.5Sn-3Zr-1Nb-0.3Mo-0.3Si; near α-typetitanium alloys such as Ti-8Al-1Mo-1V, Ti-2.25Al-11Sn-5Zr-1Mo-0.2Si,Ti-6Al-2Sn-4Zr-2Mo, Ti-5Al-5Sn-2Zr-2Mo-0.25Sn, Ti-6Al-2Nb-1Ta-0.8Mo,Ti-6Al-5Zr-0.5Mo-0.2Si and Ti-4.5Al-3V-2Fe-2Mo; α+β-type titanium alloyssuch as Ti-5Al-2Cr-1Fe, Ti-5Al-5Sn-5Zr-2Cr-1Fe, Ti-4Al-4Mn, Ti-3Al-2.5V,Ti-6Al-4V, Ti-6Al-4V(ELI), Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo,Ti-7Al-4Mo, Ti-5Al-2Zr-4Mo-4Cr, Ti-6Al-1.7Fe-0.1Si, Ti-6.4Al-1.2Fe,Ti-15Zr-4Nb-2Ta-2Pd, Ti-6Al-7Nb and Ti-8Mn; β-type titanium alloys suchas Ti-13V-11Cr-3Al, Ti-15Mo-5Zr, Ti-15Mo-0.2Pd, Ti-15V-3Cr-3Sn-3Al,Ti-20V-4Al-1Sn, Ti-22V-4Al and Ti-16V-4Sn-3Al-3Nb; near β-type titaniumalloys such as Ti-10V-2Fe-3Al and Ti-9.5V-2.5Mo-3Al; zirconium alloyssuch as zircaloy-2, zircaloy-4, Zr-2.5Nb and ozenite. Among thesemetals, titanium-containing metals are preferable and industrial puretitanium or an anticorrosion titanium alloy is more preferable.

[0154] In the process of this invention, a separator in the firstseparation step may be made of an appropriate known material. In apreferable separator, the inner wall is at least partly made of (I) ametal and/or its oxide containing at least one selected from the groupconsisting of titanium and zirconium or (II) an inorganic glass. Use ofsuch a separator is advantageous because it may prevent solid formationand line clogging. Examples of a separator include those entirely madeof a metal containing titanium or zirconium; those whose inner wall isat least partially coated with a metal containing titanium or zirconiumor its oxide; those entirely made of an inorganic glass; and those whoseinner wall is coated with an inorganic glass.

[0155] Examples of a metal containing titanium or zirconium may be asdescribed in the 1,3-dimethyl-2-imidazolidinone preparation step. Amongthese metals, a titanium-containing metal is preferable and industrialpure titanium or an anticorrosion titanium alloy is more preferable.

[0156] An inorganic glass in this invention means an inorganic materialin a glass state, including element glasses, hydrogen-bonding glasses,oxide glasses, fluoride glasses, chloride glasses, sulfide glasses,carbonate glasses, nitrate glasses and sulfate glasses.

[0157] Among these, preferable glasses are oxide glasses such assilicate glasses, phosphate glasses and borate glasses. More preferableglasses are silicate glasses such as quartz glass; alkali-silicateglasses such as water glass; soda-lime glasses such as sheet glass andcrown glass; potash-lime glasses such as Bohemian glass and crystalglass; lead glasses such as flint glass; barium glasses such as bariumflint glass; and silicate glasses such as borosilicate glass. Furtherpreferable glasses include silicate glass, soda-lime glass and soda-limeglass containing aluminum, magnesium or calcium ions as modificationions.

[0158] In the process of this invention, a hydrolysis reactor in thehydrolysis step may be made of an appropriate known material. Preferablyis used a hydrolysis reactor, whose inner wall is at least partly madeof (I) a metal and/or its oxide containing at least one selected fromthe group consisting of titanium and zirconium or (II) an inorganicglass. Use of such a hydrolysis reactor is advantageous because it mayprevent solid formation and line clogging. Examples of such a hydrolysisreactor include those entirely made of a metal containing titanium orzirconium; those whose inner wall is at least partially coated with ametal containing titanium or zirconium or its oxide; those entirely madeof an inorganic glass; and those whose inner wall is coated with aninorganic glass.

[0159] Examples of a metal containing titanium or zirconium may be asdescribed in the 1,3-dimethyl-2-imidazolidinone preparation step. Amongthese metals, a titanium-containing metal is preferable and industrialpure titanium or an anticorrosion titanium alloy is more preferable.

[0160] Inorganic glasses which may be used are as described for theseparator. Among these, preferable glasses are oxide glasses such assilicate glasses, phosphate glasses and borate glasses. More preferableglasses are silicate glasses such as quartz glass; alkali-silicateglasses such as water glass; soda-lime glasses such as sheet glass andcrown glass; potash-lime glasses such as Bohemian glass and crystalglass; lead glasses such as flint glass; barium glasses such as bariumflint glass; and silicate glasses such as borosilicate glass. Furtherpreferable glasses include silicate glass, soda-lime glass and soda-limeglass containing aluminum, magnesium or calcium ions as modificationions.

[0161] A style of a unit operation such as a reaction and separation inthe process of this invention may be, but not limited to, a batch,semi-batch or continuous system.

[0162] The process of this invention allows byproducts to be effectivelyprocessed and DMI to be prepared with a higher efficiency.

[0163] This invention will be specifically described with reference to,but not limited to, examples. In the following examples, a fraction in aseparation step or an absorption liquid in an absorption step areindicated, for instance, as follows: “the first fraction/the firstseparation step”, “the second fraction/the first separation step”, and“the absorption liquid/the absorption step.”

EXAMPLE 1

[0164] In an autoclave with an inner volume of 400 cc whose lid,stirring rod and stirring blade were made of industrial pure titanium ofJIS Group 2 and whose body was lined with industrial pure titanium ofJIS Group 2 were charged 111.4 g of methylamine methylcarbamate (1050mmol), 32.4 g of ion-exchange water (1800 mmol). The gases phase wasreplaced with nitrogen and then 13.2 g of ethylene oxide (300 mmol) and33.0 g of carbon dioxide (750 mmol) were charged. The autoclave wasexternally heated with stirring for reacting the mixture at an internaltemperature of 100° C. for 3 hours. Then, the internal temperature wasraised to 200° C. and the mixture was reacted at the same temperaturefor 7 hours, during which the maximum pressure was 9.2 MPa.

[0165] After cooling the autoclave to an ambient temperature, thereaction mixture was opened to the atmospheric pressure. The reactionmixture was collected for analyzing by gas chromatography. An yield ofDMI based on ethylene oxide was 46%.

EXAMPLE 2

[0166] [1,3-dimethyl-2-imidazolidinone Preparation Step (1st Time)]

[0167] In the autoclave described in Example 1 were charged thematerials as described in Example 1. The autoclave was externally heatedwith stirring and the mixture was reacted at an internal temperature of220° C. for 4 hours, during which the pressure was 11.0 MPa.

[0168] The autoclave was cooled to an ambient temperature and opened tothe atmospheric pressure to give 158.3 of the reaction mixture.

[0169] The collected reaction mixture was analyzed by gas chromatographyand Karl Fischer method. An yield of DMI based on ethylene oxide was57%. The reaction mixture contained 0.44 g of ammonia and ammonia partin its carbon dioxide compound (hereinafter, collectively referred to as“ammonia component”); 36.8 g of monomethylamine and monomethylamine partin its carbon dioxide compound (hereinafter, collectively referred to as“monomethylamine component”); 1.12 g of dimethylamine and dimethylaminepart of its carbon dioxide compound (hereinafter, collectively referredto as “dimethylamine component”); 0.11 g of trimethylamine andtrimethylamine part in its carbon dioxide compound (hereinafter,collectively referred to as “trimethylamine component”); 19.4 g of1,3-dimethyl-2-imidazolidinone; 0.20 g of 2-(methylamino)ethanol and2-(methylamino)ethanol part in its carbon dioxide compound (hereinafter,collectively referred to as “2-(methylamino)ethanol component”); 0.41 gof 1,3-dimethylpiperazine; 0.20 g of N,N′-dimethylethylenediamine andN,N′-dimethylethylenediamine part in its carbon dioxide compound(hereinafter, collectively referred to as “N,N′-dimethylethylenediaminecomponent”); 0.44 g of N,N-dimethylethanolamine; 1.05 g of1-methyl-2-imidazolidinone; 2.57 g of N-methyldiethanolamine; 22.5 g of1,3-dimethylurea; 43.9 g of water; and 27.4 g of carbon dioxide, carbondioxide part of carbon dioxide compound of ammonia and carbon dioxidepart of carbon dioxide compound of the above amines (monomethylamine,dimethylamine, trimethylamine, 2-(methylamino)ethanol andN,N′-dimethylethylenediamine) (hereinafter, collectively referred to as“carbon dioxide component”).

Comparative Example 1

[0170] In the autoclave described in Example 1 were charged 88.6 g ofmethylamine methylcarbamate (835 mmol) and 52.2 g of ion-exchange water(2896 mmol). After the gaseous phase was replaced with nitrogen, 26.4 gof ethylene oxide (600 mmol) and 2.2 g of carbon dioxide (52 mmol). Theautoclave was externally heated with stirring and the mixture wasreacted at an internal temperature of 100° C. for 3 hours. The mixturewas further heated to an internal temperature of 220° C., and reacted atthe same temperature for 4 hours, during which the pressure was 3.3 MPa.The reaction mixture was collected and analyzed by gas chromatography asdescribed in Example 1. An yield of DMI based on ethylene oxide was 16%.

Example 3

[0171] [The First Separation Step]

[0172] To a three-necked borosilicate glass flask with an inner volumeof 500 cc was placed 157.5 g of the reaction mixture collected in the1,3-dimethyl-2-imidazolidinone preparation step (1st time) in Example 2.Under an atmospheric pressure, it was purified by simple distillation atan internal temperature of 80 to 117° C. to obtain 73.0 g of a fraction(the first fraction/the first separation step) from a distillationcolumn. The first fraction/the first separation step was analyzed by gaschromatography and Karl Fischer method. The mixture contained 0.42 g ofthe ammonia component, 34.9 g of the monomethylamine component, 1.1 g ofthe dimethylamine component, 0.05 g of the trimethylamine component,18.6 g of the carbon dioxide component and 17.6 g of water.

[0173] The residue after simple distillation (the second fraction/thefirst separation step) was analyzed by gas chromatography and KarlFischer method. The residue contained 18.8 g of1,3-dimethyl-2-imidazolidinone, 22.0 g of 1,3-dimethylurea, 25.3 g ofwater, 0.20 g of 2-(methylamino)ethanol and 1.03 g of1-methyl-2-imidazolidinone.

[0174] [The Second Separation Step]

[0175] The second fraction/the first separation step was distilled undera reduced pressure at 64 to 66° C./230 torr (31 kPa) to collect 27.0 gof a fraction containing water (the first fraction/the second separationstep). The fraction was analyzed by gas chromatography and contained0.27 g of 1,3-dimethylpiperazine, 0.19 g ofN,N′-dimethylethylenediamine, 0.38 g of N,N-dimethylaminoethanol and0.19 g of 2-(methylamino)ethanol. The residue (the second fraction/thesecond separation step) was 43.8 g, containing 18.3 g of1,3-dimethyl-2-imidazolidinone, 21.5 g of 1,3-dimethylurea and 2.5 g ofN-methyldiethanolamine.

[0176] [The Third Separation Step]

[0177] The residue collected from the flask in the second separationstep (the second fraction/the second separation step) was distilledunder a pressure at 105 to 109° C./19.5 torr (2.5 kPa) to collect 16.8 gof a fraction containing 1,3-dimethyl-2-imidazolidinone with a purity of99%.

[0178] [The Fourth Separation Step (Stage 1)]

[0179] The fraction collected in the first separation step (the firstfraction/the first separation step) was placed in a three-necked flaskwith an inner volume of 200 mL. The flask was externally cooled by icewhile 30 g of dry ice was slowly added until the system was saturatedwith carbon dioxide. Then, the top of the three-necked flask wasequipped with a condenser and a trap via glass tubes, and the trap wascooled by ice-water.

[0180] The three-necked flask was immersed in an oil bath at 120° C. Themixture was refluxed by heating for 1 hour during which the maximuminternal temperature of the flask was 93° C. After cooling to roomtemperature, 52.1 g of an aqueous solution in the flask (the secondfraction/the fourth separation step (stage 1)) was collected andanalyzed by gas chromatography and Karl Fischer method. The solutioncontained 26.3 g of the monomethylamine component, 0.0082 g of theammonia component, 0.25 g of the dimethylamine component, 13.9 g of thecarbon dioxide component and 11.3 g of water without a detectable levelof the trimethylamine component.

[0181] [The Fourth Separation Step (Stage 2)]

[0182] In a 50 mL three-necked flask was placed the first fraction/thefourth separation step (stage 1) collected in the trap containing 7.8 gof the monomethylamine component, 0.39 g of the ammonia component, 0.76g of the dimethylamine component and 0.005 g of the trimethylaminecomponent. While externally cooling the flask with ice, 20 g of dry icewas slowly added until the system was saturated with carbon dioxide.Then, the mixture was refluxed by heating for 1 hour using the apparatusas described for the fourth separation step (stage 1), during which themaximum internal temperature in the flask was 93° C. After cooling toroom temperature, 13.7 g of a solution in the flask (the secondfraction/the fourth separation step (stage 2)) was collected andanalyzed by gas chromatography and Karl Fischer method. The solutioncontained 6.1 g of the monomethylamine component, 0.0058 g of theammonia component, 0.19 g of the dimethylamine component, 3.3 g of thecarbon dioxide component and 4.1 g of water without a detectable levelof the trimethylamine component.

[0183] [1,3-dimethyl-2-imidazolidinone Preparation Step (2nd Time)]

[0184] In the autoclave as described in the1,3-dimethyl-2-imidazolidinone preparation step (1st time) was charged63.8 g of the aqueous solution (31.5 g of the monomethylamine component,16.7 g of the carbon dioxide component and 14.8 g of water) containingmonomethylamine (the second fraction/the fourth separation step (stage1) and the second fraction/the fourth separation step (stage 2))collected in the fourth separation step (stage 1) and the fourthseparation step (stage 2) respectively, and then charged 17.6 g ofion-exchange water and 57.6 g of methylamine methylcarbamate. Afterreplacing the gaseous phase with nitrogen, 13.2 g of ethylene oxide (300mmol) and 38.7 g of carbon dioxide were charged. That is, the materialswere charged such that the total of the molar amount of monomethylamineand the molar amount of the monomethylamine part in the carbon dioxidecompound of monomethylamine, the total of the molar amount of carbondioxide and the molar amount of the carbon dioxide part in the carbondioxide compound of monomethylamine, and the molar amount of water wasequal to those chaeged in the 1,3-dimethyl-2-imidazolidinone preparationstep (1st time) respectively. The mixture was reacted at an internaltemperature of 220° C. for 4 hours as described for the1,3-dimethyl-2-imidazolidinone preparation step (1st time).

[0185] The reaction mixture was collected and analyzed as described forthe 1,3-dimethyl-2-imidazolidinone preparation step (1st time). An yieldof DMI based on ethylene oxide was 56%. The reaction mixture contained1.1 g of 1-methyl-2-imidazolidinone and 0.45 g of the ammonia component.

Comparative Example 2

[0186] In the 1,3-dimethyl-2-imidazolidinone preparation step (2nd time)in Example 3, 72.0 g of the first fraction/the first separation step(34.4 g of the monomethylamine component, 0.41 g of the ammoniacomponent, 1.05 g of the dimethylamine component, 18.3 g of the carbondioxide component and 17.4 g of water) was charged in place of thesecond fraction/the fourth separation step (stage 1) and the secondfraction/the fourth separation step (stage 2). Furthermore, materialswere charged so that the amounts of monomethylamine component, thecarbon dioxide component, water and ethylene oxide were equal to thosecharged in the 1,3-dimethyl-2-imidazolidinone preparation step (2ndtime) in Example 3. Reaction and analysis were conducted as describedfor the 1,3-dimethyl-2-imidazolidinone preparation step (2nd time) inExample 3. An yield of DMI based on ethylene oxide was 50%. The reactionmixture contained 2.1 g of 1-methyl-2-imidazolidinone and 0.86 g of theammonia component.

[0187] As described above, monomethylamine collected in the fourthseparation step may be circulated for recycling to prevent increase ofbyproducts and provide DMI with a higher yield.

Example 4

[0188] [The First Reaction Step (1st time)]

[0189] In the autoclave as described in Example 1 was charged 37.8 g ofion-exchange water (2100 mmol). After replacing the gaseous phase withnitrogen, 93.2 g of monomethylamine (3000 mmol) and 23.8 g of carbondioxide (540 mmol) were charged. The autoclave was externally heated toan internal temperature of 100° C. with stirring. After the internaltemperature reached 100° C., 13.2 g of ethylene oxide (300 mmol) wasadded, and the mixture was heated at an internal temperature of 100° C.for 1 hour.

[0190] [The Seventh Separation Step]

[0191] The autoclave in the first reaction step (1st time) was cooled to70° C., and was gradually opened to the atmospheric pressure whilemonomethylamine was collected from the gaseous phase into a pressurebottle with an inner volume of 200 cc cooled to −78° C. (the firstfraction/the seventh separation step) to provide 42.7 g ofmonomethylamine.

[0192] [The Second Reaction Step (1st Time)]

[0193] Gas chromatography for the residual reaction mixture in theautoclave in the seventh separation step (the second fraction/theseventh separation step) indicated that no ethylene oxide existed andthat yields for 2-(methylamino) ethanol and N-methyldiethanolamine basedon ethylene oxide were 85% and 15%, respectively. The reaction mixturecontained 19.2 of the 2-(methylamino)ethanol component, 2.68 g of theN-methyldiethanolamine component, 41.8 g of the monomethylaminecomponent, 37.8 g of water and 23.8 g of the carbon dioxide component.

[0194] Then, 16.4 g of ion-exchange water (913 mmol), 14.3 g ofmonomethylamine (461 mmol) and 55.6 g of carbon dioxide (1263 mmol) werecharged in the autoclave containing the reaction mixture (the secondfraction/the seventh separation step) comprising 19.0 g of the2-(methylamino)ethanol component, 2.67 g of the N-methyldiethanolamine,41.6 g of the monomethylamine component, 23.6 g of the carbon dioxidecomponent and 37.6 g of water. The mixture was reacted at an internaltemperature of 200° C. for 5 hours, during which the maximum pressurewas 8.3 MPa.

[0195] After cooling the autoclave to room temperature, it was opened tothe atmospheric pressure to collect 176.2 g of the reaction mixture.

[0196] The reaction mixture was analyzed by gas chromatography and KarlFischer method, indicating that an yield for1,3-dimethyl-2-imidazolidinone was 76% based on ethylene oxide. Thereaction mixture contained 0.35 g of the ammonia component, 32.1 g ofthe monomethylamine component, 0.88 g of the dimethylamine component,0.11 g of the trimethylamine component, 26.0 g of1,3-dimethyl-2-imidazolidinone, 0.64 g of the 2-(methylamino)ethanolcomponent, 0.77 g of 1,3-dimethylpiperazine, 0.69 g of theN,N′-dimethylethylenediamine component, 0.42 g ofN,N-dimethylethanolamine, 0.42 g of 1-methyl-2-imidazolidinone, 1.34 gof N-methyldiethanolamine, 20.3 g of 1,3-dimethylurea, 67.1 g of waterand 24.3 g of the carbon dioxide component.

[0197] [The First Separation Step and an Absorption Step]

[0198] In a borosilicate glass three-necked flask with an inner volumeof 500 cc was placed 174.4 g of the reaction mixture collected in thesecond reaction step (1st time). The mixture was simply distilled underan ambient pressure at an internal temperature of 80 to 117° C. while afraction from a distillation column was contacted with and absorbed in10 g of ion-exchange water in a flask with an inner volume of 200 cc toobtain 86.4 g of an aqueous solution containing the fraction. Theaqueous solution (absorption solution/absorption step) was analyzed bygas chromatography and Karl Fischer method. It contained 0.34 g of theammonia component, 31.5 g of the monomethylamine component, 0.86 g ofthe dimethylamine component, 0.11 g of the trimethylamine component,16.7 g of the carbon dioxide component and 36.9 g of water.

[0199] The residue after the simple distillation (the secondfraction/the first separation step) was also analyzed by gaschromatography and Karl Fischer method. The residue contained 25.2 g of1,3-dimethyl-2-imidazolidinone, 19.9 g of 1,3-dimethylurea, 38.8 g ofwater, 0.63 g of 2-(methylamino)ethanol and 0.42 g of1-methyl-2-imidazolidinone.

[0200] [The Second Separation Step]

[0201] The second fraction/the first separation step was distilled invacuo at 64 to 66° C./230 torr (31 kPa) to collect 40.5 g of awater-containing fraction (the first fraction/the second separationstep). The fraction was analyzed by gas chromatography, indicating thatit contained 0.51 g of 1,3-dimethylpiperazine, 0.66 g ofN,N′-dimethylethylenediamine, 0.36 g of N,N-dimethylaminoethanol and0.61 g of 2-(methylamino)ethanol. The distillation left 46.2 g of aresidue (the second fraction/the second separation step) containing 24.5g of 1,3-dimethyl-2-imidazolidinone, 19.5 g of 1,3-dimethylurea and 1.3g of N-methyldiethanolamine.

[0202] [The Third Separation Step]

[0203] The residue collected from the flask in the second separationstep (the second fraction/the second separation step) was distilled invacuo at 105 to 109° C./19.5 torr (2.5 kPa) to collect 22.6 g of1,3-dimethyl-2-imidazolidinone with a purity of 99% as adistillate (thefirst fraction/the third separation step).

[0204] [The Fourth Separation Step (Stage 1)]

[0205] In a three-necked flask with an inner volume of 200 mL was placedthe aqueous solution containing the fraction collected in the firstseparation step (absorption solution/absorption step). While externallycooling the flask with ice, 30 g of dry ice was slowly added until thesystem was saturated with carbon dioxide. Then, the top of thethree-necked flask was equipped with a trap containing 10 g ofion-exchange water via a glass tube, and the trap was cooled byice-water.

[0206] The three-necked flask was immersed in an oil bath at 120° C.,and the mixture was refluxed by heating for 1 hour during which themaximum internal temperature of the flask was 93° C. After cooling toroom temperature, 54.3 g of an aqueous solution in the flask (the secondfraction/the fourth separation step (stage 1)) was collected andanalyzed by gas chromatography and Karl Fischer method. The solutioncontained 23.7 g of the monomethylamine component, 0.0068 g of theammonia component, 0.20 g of the dimethylamine component, 12.5 g of thecarbon dioxide component and 17.3 g of water without a detectable levelof the trimethylamine component.

[0207] [The Fourth Separation Step (Stage 2)]

[0208] In a 200 mL three-necked flask was placed the aqueous solution ofthe first fraction/the fourth separation step (stage 1) collected in thetrap. This solution contained 7.1 g of the monomethylamine component,0.32 g of the ammonia component, 0.63 g of the dimethylamine componentand 0.072 g of the trimethylamine component. While externally coolingthe flask with ice, 20 g of dry ice was slowly added until the systemwas saturated with carbon dioxide. Then, the mixture was refluxed byheating for 1 hour using the apparatus as described for the fourthseparation step (stage 1), during which the maximum internal temperaturein the flask was 93° C. After cooling to room temperature, 21.8 g of asolution in the flask (the second fraction/the fourth separation step(stage 2)) was collected and analyzed by gas chromatography and KarlFischer method. The solution contained 5.6 g of the monomethylaminecomponent, 0.0049 g of the ammonia component, 0.16 g of thedimethylamine component, 3.0 g of the carbon dioxide component and 12.9g of water without a detectable level of the trimethylamine component.

[0209] An aqueous solution containing 74.0 g of monomethylamine (thesecond fraction/the fourth separation step) was obtained as the total ofthe second fraction/the fourth separation step (stage 2) and the secondfraction/the fourth separation step (stage 1).

[0210] [The First Reaction Step (2nd time)]

[0211] In the autoclave as described in the first reaction step (1sttime) was charged 69.5 g of the aqueous solution containingmonomethylamine (the second fraction/the fourth separation step) (26.9 gof the monomethylamine component, 14.2 g of the carbon dioxide componentand 27.5 g of water) collected in the fourth separation step (stage 1)and the fourth separation step (stage 2), and then 10.3 g ofion-exchange water. After replacing the gaseous phase with nitrogen,42.5 g of the first fraction/the seventh separation step collected inthe seventh separation step, 23.8 g of monomethylamine and 9.5 g ofcarbon dioxide were charged. That is, the materials were charged suchthat the total of the molar amount of monomethylamine and the molaramount of the monomethylamine part in the carbon dioxide compound ofmonomethylamine, the total of the molar amount of carbon dioxide and themolar amount of the carbon dioxide part in the carbon dioxide compoundof monomethylamine, and the molar amount of water was equal to thosecharged in the first reaction step (1st time). With stirring, theautoclave was externally heated to an internal temperature of 100° C.After the internal temperature reached 100° C., 13.2 g of ethylene oxide(0.3 mol) was added and heating was continued at an internal temperatureof 100° C. for 1 hour.

[0212] The reaction mixture was collected and analyzed by gaschromatography as described in the second reaction step (1st time),indicating that an conversion ratio of ethylene oxide was 100% andyields of 2-(methylamino)ethanol and N-methyldiethanolamine were 85% and15%, respectively, based on ethylene oxide newly charged in the firstreaction step (2nd time).

[0213] [The Second Reaction Step (2nd Time)]

[0214] To the reaction mixture left in the autoclave in the firstreaction step (2nd time) containing 18.9 g of the 2-(methylamino)ethanolcomponent, 2.65 g of N-methyldiethanolamine, 41.7 g of themonomethylamine component, 23.8 g of the carbon dioxide component and37.8 g of water were added 4.5 g of the monomethylamine-containingaqueous solution comprising 1.76 g of the monomethylamine component,0.93 g of the carbon dioxide component and 1.80 g of water (the secondfraction/the fourth separation step) collected in the fourth separationstep (stage 1) and the fourth separation step (stage 2); 21.0 g of theresidue containing 17.8 g of 1,3-dimethylurea in the third separationstep (the second fraction/the third separation step); and then 18.3 g ofion-exchange water. After replacing the gaseous phase with nitrogen,45.8 g of carbon dioxide was charged. That is, the following a) to c)were charged in an equal amount to that in the second reaction step (1sttime), respectively:

[0215] a) the total of the molar amount of monomethylamine, the molaramount of the monomethylamine part in the carbon dioxide compound ofmonomethylamine and the double of the molar amount of 1,3-dimethylurea,

[0216] b) the total of the molar amount of carbon dioxide, the molaramount of the carbon dioxide part in the carbon dioxide compound ofmonomethylamine, the molar amount of the carbon dioxide part in thecarbon dioxide compound of 2-(methylamino)ethanol and the molar amountof 1,3-dimethylurea, and

[0217] c) a difference between the molar amount of water and the molaramount of 1,3-dimethylurea.

[0218] The mixture was reacted at an internal temperature of 200° C. for5 hours as described in the second reaction step (1st time).

[0219] The reaction mixture was collected and analyzed as described inthe second reaction step (1st time), indicating that an yield of1,3-dimethyl-2-imidazolidinone was 76% based on ethylene oxide newlycharged in the first reaction step (2nd time).

[0220] Industrial Applicability

[0221] As described above, the process of this invention is suitable forindustrially preparing a 1,3-dialkyl-2-imidazolidinones using anindustrially readily available alkylene oxide as a starting material. Inparticular, in a process for preparing 1,3-dimethyl-2-imidazolidinone,1,3-dimethyl-2-imidazolidinone can be prepared with a higher efficiencywhile effectively separating and processing byproducts such asN-methyldiethanolamine, ammonia, dimethylamine, trimethylamine,1-methyl-2-imidazolidinone and 1,3-dimethylurea.

1. A process for preparing a 1,3-dialkyl-2-imidazolidinone by using analkylene oxide represented by formula (1) as a first component

wherein in the formula (1), R¹ represents hydrogen or alkyl group having1 to 6 carbon atoms, using at least one selected from the groupconsisting of the following components (A), (B) and (C) as a secondcomponent: component (A): carbon dioxide and a monoalkylaminerepresented by formula (2): R²NH₂  (2) wherein in the formula (2),R²represents alkyl group having 1 to 6 carbon atoms; component (B): acarbon dioxide compound of the monoalkylamine represented by formula(2); and component (C): an 1,3-dialkylurea represented by formula (3):R²NHCONHR²  (3) wherein in the formula (3), R² is as defined above, andreacting said first component with said second component by heatingthose components at 50° C. or higher to give1,3-dialkyl-2-imidazolidinone represented by formula (4):

wherein in the formula (4), R¹ and R² are as defined above,characterized in that the total molar amount of a molar feed amount ofthe monoalkylamine included in the component (A), a molar feed amount ofthe monoalkylamine part of the carbon dioxide compound ofmonoalkylamine, said compound being component (B), and the double of amolar feed amount of the 1,3-dialkylurea, said 1,3-dialkylurea beingcomponent (C), is at least three folds of a molar feed amount of saidalkylene oxide.
 2. The process as claimed in claim 1, characterized inthat the reaction is conducted under a pressure of 4 MPa or higher. 3.The process as claimed in claim 1 or 2, characterized in that the totalmolar amount of a molar feed amount of the carbon dioxide included inthe component (A), a molar feed amount of the carbon dioxide part of thecarbon dioxide compound of monoalkylamine, said compound being thecomponent (B), and a molar feed amount of the 1,3-dialkylurea, said1,3-dialkylurea being the component (C), is at least one and half foldsof a molar feed amount of said alkylene oxide.
 4. The process as claimedin any of claims 1 to 3, characterized in that R¹ is hydrogen atom; R²represents methyl; and the 1,3-dialkyl-2-imidazolidinone prepared is1,3-dimethyl-2-imidazolidinone.
 5. The process as claimed in claim 4,characterized in that ethylene oxide is used as said first component andat least one selected from the group consisting of the followingcomponents (D), (E) and (F) is used as said second component: component(D): carbon dioxide and monomethylamine; component (E): a carbon dioxidecompound of monomethylamine; and component (F): 1,3-dimethylurea, theprocess comprises: (1) a 1,3-dimethyl-2-imidazolidinone preparation stepof preparing 1,3-dimethyl-2-imidazolidinone by heating said firstcomponent and said second component at 50° C. or higher, and the processfurther comprises: (2) a first separation step of separating thereaction mixture obtained in the 1,3-dimethyl-2-imidazolidinonepreparation step into a first fraction containing monomethylamine,carbon dioxide and a carbon dioxide compound of monomethylamine as maincomponents, and also containing water; and a second fraction containing1,3-dimethyl-2-imidazolidinone and high-boiling compounds with a higherboiling point than that of 1,3-dimethyl-2-imidazolidinone as maincomponents, and also containing water; (3) a second separation step ofseparating at least part of the second fraction in the first separationstep into a first fraction containing water and low-boiling amines witha boiling point higher than that of water and lower than that of1,3-dimethyl-2-imidazolidinone as main components; and a second fractioncontaining 1,3-dimethyl-2-imidazolidinone and said high-boilingcompounds as main components; (4) a third separation step of separatingthe second fraction in the second separation step into a first fractioncontaining 1,3-dimethyl-2-imidazolidinone as a main component; and asecond fraction containing said high-boiling compounds as maincomponents; and (5) a fourth separation step of separating the firstfraction in the first separation step into a first fraction containingammonia, dimethylamine, trimethylamine, a carbon dioxide compound ofammonia, a carbon dioxide compound of dimethylamine and a carbon dioxidecompound of trimethylamine as main components, and also containingwater; and a second fraction containing monomethylamine and a carbondioxide compound of monomethylamine as main components, and alsocontaining water, where at least part of the second fraction in thefourth separation step is supplied in the 1,3-dimethyl-2-imidazolidinonepreparation step.
 6. The process as claimed in claim 5, characterized inthat the 1,3-dimethyl-2-imidazolidinone preparation step is carried outby: (6) a first reaction step of heating ethylene oxide and at least oneselected from the group consisting of the components (D), (E) and (F) at50° C. or higher to prepare N-methyldiethanolamine and2-(methylamino)ethanol; and (7) a second reaction step of heatingN-methyldiethanolamine and 2-(methylamino)ethanol prepared in the firstreaction step with at least one selected from the group consisting ofthe components (D), (E) and (F) at 100° C. or higher to prepare1,3-dimethyl-2-imidazolidinone, and the second fraction in the fourthseparation step is supplied in said first reaction step and/or saidsecond reaction step.
 7. The process as claimed in claim 5 or 6,characterized in that in the fourth separation step, at least part ofthe first fraction in the first separation step is contacted with carbondioxide, heated at 50° C. or higher, and separated by vapor-liquidseparation to remove the first fraction in the fourth separation stepinto the gaseous phase and obtain the second fraction in the fourthseparation step from the liquid phase.